lib: initialize output pointers to NULL before calling strto[ff,l,ul]
In order to make MSAN happy:
==2200945==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x596f3b3ed246 in curlx_strtoofft [...]/libcurl/src/lib/strtoofft.c:239:11
#1 0x596f3b402156 in Curl_httpchunk_read [...]/libcurl/src/lib/http_chunks.c:149:12
#2 0x596f3b348550 in readwrite_data [...]/libcurl/src/lib/transfer.c:607:11
[...]
==2202041==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x5a3fab66a72a in Curl_parse_port [...]/libcurl/src/lib/urlapi.c:547:8
#1 0x5a3fab650645 in parse_authority [...]/libcurl/src/lib/urlapi.c:796:12
#2 0x5a3fab6740f6 in parseurl [...]/libcurl/src/lib/urlapi.c:1176:16
#3 0x5a3fab664fc5 in parseurl_and_replace [...]/libcurl/src/lib/urlapi.c:1342:12
[...]
==2202320==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x569076a0d6b0 in ipv4_normalize [...]/libcurl/src/lib/urlapi.c:683:12
#1 0x5690769f2820 in parse_authority [...]/libcurl/src/lib/urlapi.c:803:10
#2 0x569076a160f6 in parseurl [...]/libcurl/src/lib/urlapi.c:1176:16
#3 0x569076a06fc5 in parseurl_and_replace [...]/libcurl/src/lib/urlapi.c:1342:12
[...]
Signed-off-by: Louis Solofrizzo <lsolofrizzo@scaleway.com>
Closes #12995